1. Field of the Invention
This invention relates to sample collection tubes provided with a test fluid safety separator, permitting pre-loading of the tubes with potentially toxic testing reagents. More particularly, this invention relates to a closed system for the collection, preparation and stabilization of nucleic acid, comprising a separator device, and method for collecting and transporting fluid samples whereby the separator reduces back flow of potentially toxic testing solutions, reduces the opportunity for contamination and increases amount of target recovered.
2. Description of Related Art
In blood collection procedures, samples of whole blood are typically collected from a patient by venipuncture through a cannula or needle attached to a syringe or an evacuated collection tube. Typically, the samples are then shipped to a laboratory where personnel experienced in sample preparation add testing reagents such as a lysing solution, and then place the tube in a centrifuge so as to effect mixing of the blood sample with the reagent. Lysing solutions, or other testing reagents, are often toxic, and hence are not included in the sample collection tube because of the possibility of back flow into the veins of the patient during sample collection. Thus, typically, laboratory personnel open the collection tube to add the testing reagent to the collected specimen. This is time consuming and also increases the risk of sample contamination.
In another diagnostic area, a patient""s whole blood sample maybe separated into two liquid phases, and separately maintain for subsequent examination of the individual components. A variety of separator devices have been used in collection devices to separate the heavier and lighter phases of a fluid sample.
However, to employ a separator device in an evacuated tube for the collection of fluid samples it is desirable that the separator device: (i) is easily and safely used for collecting samples; (ii) is independent of temperature during storage and shipping and stable to radiation sterilization; (iii) permits completion of nucleic acid preparation by centrifugation alone (with no additional step of introducing testing reagents); (iv) minimizes opportunity for cross contamination of samples from introduction of testing solutions before centrifugation; (v) increases the amount of target than can be recovered. Presently known separator devices do not meet all of these requirements.
The present invention comprises a closed system for the collection and testing of a fluid sample preferably a blood sample including the preparation and stabilization of nucleic acids. The system includes a method and an assembly for collection and testing. Preferably, the assembly comprises a container and a safety separator.
Most preferably, the container is a tube and the separator is arranged to move in the tube under the action of centrifugal force in order to release a testing solution up, into the fluid sample.
Most, preferably, the tube includes an open end, a closed end and a sidewall extending between the open end and closed end. The tube further includes a closure with a releasable self-sealing septum disposed to fit in the open end of the tube. A safety separator is positioned atop preloaded testing reagents in the bottom of the tube. Alternatively, both ends of the tube may be open, and both ends of the tube may be sealed by elastomeric closures. At least one of the closures of the tube may include a needle pierceable resealable septum.
In one preferred embodiment, the safety separator comprises a toroidal separator and in another preferred embodiment, a bellow separator.
Preferably, the safety separator includes an overall specific gravity greater than the specific gravity of the testing reagents (preloaded into the tube) or the mixture of testing reagents and the sample.
According to a desired method of the present invention, testing reagents are provided in a typical sample collection evacuated tube. Thereafter, a separator is placed in the tube, above the test reagents. The separator makes physical contact with the tube, presenting a barrier to back flow of the test reagents during sample collection. A resealable closure is placed in the end of the tube so as to create an evacuated space between the closure and the separator. A sample is collected in the evacuated space. Under centrifugal force, the separator is deformed and the barrier with the tube is broken. Because the separator""s density is greater than that of the testing reagents, it begins to migrate toward the closed end of the tube, releasing testing solution to mix with the sample collected.